光纤接入网技术综述Overview of optical fiber access network technology.docx

光纤接入网技术综述Overview of optical fiber access network technology.docx

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光纤接入网技术综述Overviewofopticalfiberaccessnetworktechnology

光纤接入网技术综述（Overviewofopticalfiberaccessnetworktechnology）

Fromtheperspectiveoftheentiretelecommunicationnetwork,theentirenetworkcanbedividedintothepublicnetworkanduserhomenetwork,twolarge,theCPNbelongstoallusers,thus,usualpartoftelecommunicationnetworkreferstothepublictelecommunicationnetworks.Thepublictelecommunicationnetworkcanbedividedintolongdistancenetwork,relaynetworkandaccessnetwork3parts.Thecombinationoflongdistancenetworkandrelaynetworkiscalledthecorenetwork.Relativetothecorenetwork,accessnetworkbetweenlocalswitchandtheuser,mainlytocompletetheuseraccesstocorenetwork,accessnetworknodeinterface（SNI）bybusinessandusernetworkinterface（UNI）ofaseriesoftransmissionequipment.

Inrecentyears,thenewtechnologicalrevolutionrepresentedbyInternetisprofoundlychangingthetraditionaltelecommunicationconceptandsystemstructure,ascountriesaccessnetworkmarketgraduallyopening,therelaxationofthetelecomregulationpolicy,competitionisincreasinglyintensifiedandexpanded,therapidemergenceofnewbusinessrequirements,cabletechnology,includingopticalfibertechnologyandthedevelopmentofwirelesstechnology,accessnetworkhasbecomethefocusofattention.Withthehugemarketpotential,thereareallkindsofaccessnettechnologies.Opticalfibercommunicationhastheadvantagesofhighcommunicationcapacity,highquality,stableperformance,anti-electromagneticinterferenceandstrongconfidentiality.Opticalfiberplaysanimportantroleinmainlinecommunication.Intheaccessnetwork,opticalfiberaccesswillalsobethefocusofdevelopment.Opticalfiberaccessnetworkisalong-termsolutiontodevelopbroadbandaccess.

1.Basiccompositionofopticalfiberaccessnetwork

Opticalfiberaccessnetwork（OAN）referstothetransmissionfunctionoftheaccessnetworkwithopticalfiberasthemaintransmissionmedium.Connecttothebusinessnodethroughtheopticallineterminal（OLT）,connectedtotheuserthroughtheopticalnetworkunit（ONU）.Opticalfiberaccessnetworksincluderemotedevices-opticalnetworkunitsandinsetdevices-opticallineterminalsthatareconnectedthroughtransmissiondevices.ThemaincomponentsofthesystemareOLTandthedistalONU.Theycompletethetransitionfromthebusinessnodeinterface（SNI）totheusernetworkinterface（UNI）intheentirenetwork.Theaccessdeviceitselfhastheabilitytonetwork,whichcanformavarietyofnetworktopologies.Accessdevicesatthesametimealsohavelocalmaintenanceandremotecentralizedmonitoringfunction,lighttransmissionthroughthetransparentformamaintenancemanagementnetwork,andthroughthecorrespondingnetworkmanagementprotocolinnetworkmanagementcenterandunifiedmanagement.

OLT'sroleistoprovidetheinterfacebetweenthenetworkandthelocalswitch,andtocommunicatewiththeopticalnetworkunitoftheclientthroughopticaltransmission.Itseparatestheswitchingfunctionoftheswitchfromtheuseraccess.Theopticalcircuitterminalprovidesmaintenanceandmonitoringforitselfandtheuser,whichcanbeplaceddirectlywiththelocalswitchandcanbesetattheremoteend.

ONU'sroleistoprovidetheusersideinterfacefortheaccessnetwork.Itcanbeconnectedtomultipleuserterminals,withthecapabilityofphotoelectricconversionandcorrespondingmaintenanceandmonitoring.ThemainfunctionofONUistoendopticalfiberfromOLT,dealwithopticalsignalsandprovidebusinessinterfacesformanysmallbusinesses,businessusersandresidentialusers.ONU'snetworkendistheopticalinterface,anditsclientistheelectricalinterface.SotheONUhaslight/electricityandpower/lightconversioncapabilities.Italsohasthefunctionofnumber/modeandmode/numberconversionofvoice.TheONUisusuallyplacedclosetotheuser,

Itspositionhasgreatflexibility.

ThefibreopticaccessNetwork（OAN）isdividedintotwoclasses:

AON,ActiveOpticalNetwork,andthepassiveopticalNetwork（PON,PassiveOpticaOpticalNetwork）.

Two,activeopticalfiberaccessnetwork

TheactiveopticalnetworkcanbedividedintoSDHbasedAONandPDHbasedAON.Bureauofactiveopticalnetworkterminalequipment（CE）andtheremoteequipmentconnectedto（RE）throughactiveopticaltransmissionequipment,hasbeenextensivelyusedintransmissiontechnologyisthebackboneofSDHandPDHtechnology,butisgivenprioritytowithSDHtechnology,thispaperfocusesonSDH（synchronousopticalnetwork）system.

1.TheactiveopticalnetworkbasedonSDH

TheconceptofSDHwasfirstputforwardbytheAmericanbellcommunicationsresearchinstitutein1985,iscalledsynchronousopticalnetwork（SynchronousOpticalNETworkSONET）.Itiscomposedofasetofhierarchicalstandardtransmissionstructure,suitableforallkindsoftheadaptationprocessofnetload（thatis,thenetworknodeinterfacecanbeusedinthetelecommunicationsbusinesspartofthebitstream）onphysicalmediasuchasfiberoptictransmission,microwave,satellite,etc.Thestandardwasthenewstandardfortheusdigitalsystemin1986.Theinternationaltelecommunicationunionstandardsdepartment（ITU-T）isthepredecessoroftheinternationaltelegraphandtelephoneadvisorycommittee（CCITT）acceptSONETconceptin1988,andtoreachadealwiththeassociationofAmericanstandard（ANSI）,renamedafteramendtheSONETsynchronousdigitalseries（SynchronousDigitalHierarchy,SDH）,makingitalsoadaptedtotheopticalfiber,microwave,satellitetransmissionsystemofgeneraltechnology.

SDHnetworkistheoriginalPDHnetwork（PlesiochronousDigitalHierarchyquasisynchronousdigitalseries）ofarevolution.PDHisasynchronousmultipleconnection,anynetworknodesaccessafterthebranchatlowspeedsignalshouldbeonthenodetoreceive,codeconversion,speedadjustment,timing,andtheoneyard,scramblerprocess,suchassolutionandPDHrulesontheelectricalinterface,onlyonthecircuitsystemandopticalinterfacedoesnothaveunifiedregulation,unabletorealizetheestablishmentofaglobalinformationnetwork.WiththeintroductionofSDHtechnology,thetransmissionsystemnotonlyhasthefunctionofprovidingthephysicalprocessofsignaltransmission,butalsoprovidesthefunctionofprocessingandmonitoringthesignal.SDHcontainersthroughavarietyofCandemptycontainersofVCandthedefinitionofthecompoundframestructureofthecascade,thebusinesscansupportvariouscircuitlayer,suchasvariousrateofasynchronousdigitalseries,DQDB,FDDI,ATM,etc.,andallkindsofnewbusinessinthefuture.AlargenumberofalternatechannelsinthesegmentoverheadenhancethescalabilityoftheSDHnetwork.ArtificialchangesintheoriginalPDHwiringthroughsoftwarecontrolmethodrealizesthecrossconnectionandreuseconnection,providesaflexibleup/downtheabilityofcircuit,andmakesthedynamicvariablenetworktopology,enhancetheflexibilityandsecurityofthenetworktoadapttothebusinessdevelopment,canbeinmoregeometrywithinthescopeofprotectioncircuitandoptimalutilizationofheightandcommunicationability,layafoundationtoenhancethecapacityofnetwork,itonlytakesafewsecondstonetworking.Inparticular,SDHself-healingringcanberecoveredrapidlywithinafewmillisecondsafterthecircuithasbrokendown.TheseadvantagesofSDHmakeitthebasetransmissionnetworkofbroadbandservicedigitalnetwork.

ThemainadvantageofSDH（synchronousopticalnetwork）isthatSDHcanprovideidealnetworkperformanceandbusinessreliability.TheinherentflexibilityofSDHmakestheSDHsystemespeciallysuitableforthedevelopmentofextremelyrapidcellularcommunicationsystems.Ofcourse,consideringthehighsensitivityandaccesstothecostoftherunningenvironmentofELieXing,applicabletotheaccessnetworkofSDHequipmentmustbehighlycompact,lowpowerconsumptionandlowcostofthenewsystem,itsapplicationandmarketprospectslookgood.

LatestdevelopmenttrendofaccessnetworkwithSDHistosupporttheIPaccess,atleastneedtosupportthemappingoftheEthernetinterface,soinadditiontocarryvoicetraffic,partoftheSDHnetloadcanbeutilizedtotransmitIPbusiness,sothattheSDHcanalsosupportIPaccess.TherearemanywaystosupportIPtransferinadditiontotheexistingPPPapproach,whichisalsoamoreefficientwaytosupportIPtransmission.Insummary,asamatureandreliabledeliverytechnologyprovidingthemainbusinessincome,itwillcontinuetoimprovethesmoothtransitionoftheswitchingnetworktopacketnetworkintheforeseeablefuture.

2.ActiveopticalnetworkbasedonPDH

Thequasi-synchronousdigitalseries（PDH）,withitscheapfeaturesandflexiblenetworkingfeatures,hasbeenwidelyusedinthenetwork.EspeciallyinrecentyearsintroducedSPDHequipmenttotheintroductionoftheconceptofSDHPDHsystem,furtherimprovethereliabilityandflexibilityofthesystem,theimprovementofPDHsystemforalongtime,arestillwidelyused.

3.Passiveopticalfiberaccessnetwork

Thenon-sourceopticalnetwork（PON）,whichreferstotheopticaldistributionnetwork（ODN）betweenOLTandONU,doesnothaveanyactiveelectronics,whichincludesanATM'spassiveopticalnetworkAPONandip-basedPON.

ThebusinessdevelopmentofAPONisimplementedinstages,andtheinitialstageismainlytheVPlinebusiness.Comparedwithordinarylinebusiness,APONprovidestheVPspeciallinebusinessequipmentcostlow,smallvolume,energysaving,reliablestabilityofthesystem,theperformancepricehascertainadvantages.Thesecondstepi